Variable-speed electric motor.



No. 7l3,86l. Patented Nov. l8, I902.

A. 6. DAVIS.

VARIABLE SPEED ELECTRIC IOTOR.

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Inventor? No. 7l3,86l. Patented Nov. I8, I902.

A. 6. DAVIS.

VARIABLE SPEED ELECTRIC IOTOR.

(Application 104 In. 29, 1902.

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CULtnesses Inven ton UNITED STATES PATENT OFFICE.

ALBERT G. DAVIS, OF SCHENECTADY, NEWV YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

VARIABLE-SPEED ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent N 0. 713,861, dated. November 18, 1902.

Application filed March 29, 1902.

To all whom, it may concern:

Be it known that I, ALBERT G. DAVIS, a citi- Zen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Variable-Speed Electric Motors, (Case No. 2,056,) of which the following is a specification.

This invention relates to electric motors,

and especially to those used for driving machine-tools, printing-presses, and the like, where a considerable variation of speed is desirable irrespective of the load. To avoid the undesirable effects of rheostatic control at is slow speeds and provide for a wide variation in speed, I make use of a small motor-generator to furnish currents of low voltage for starting the working motor. The motor-generator is preferably of about one-tenth the capacity'of the working motor, and as it can be run at a fairly high speed its weight can be quite small. Its driving-armature can be thrown across the line by means of a suitable controller, while the generator-armature has a coarse winding and rotates in an adjustable field. The working motor is of the ordinary direct-current type, and by means of the controller it first takes current from the motorgenerator; but after it reaches a predetermined speed it is connected directly with the line and the motor-generator stops running.

In the accompanying drawings, Figures 1 to 16, inclusive, are diagrams showing the successive steps in such a system of control,

while Fig. 17 is a diagram of a controller and its connections for such a system.

The armature of the working motor is lettered WA and its field-coil \VF. The driving-armature of the motor-generator is lettered MA and its field-coil ME. Its genera tor-armature is GA and the corresponding field-coil GF. A three-wire system of mains a" y .z' is preferably provided, though the ordinary two-wire system may be used, if desired.

The controller C comprises the usual stationary fingers and movable contact-segments to effect the desired circuit changes. The

terminals of the working-motor armature and field-coil are connected by leads 1 2 3 4 with the fingers 1 2 3 4:, respectively. The driv- Serial No. 100,572. (No model.)

ing-armature of the motor-generator is connected by leads 5 6 with the fingers 5 6 and its field-coil by leads 7 S with the fingers 7 8'. The generator-armature of the motor-generator is connected by leads 9 10 with the fingers 9 10and its field-coil by leads 11 12 with the fingers 11 12. Resistance-coils R R R are connected by leads 13 14 15 16 with the fin-- gers 13 14 1516'. The high-potential main y of the three-wire system is connected by lead 17 with the finger 17 through a circuitbreaker CB, the negative main .2 by lead 18 with the finger 18 through a blow-out magnet BM, and the the low-potential main 0; bylead 19 with the finger19throughacircuit-breaker CB. The controllencylindercarries opposite each finger one or more contact-segments arranged as follows: segments 1 2 9 10 cover positions two to five of the controller-cylin- 7o der; segmentl positions six to sixteen. Segments 2 and 12" cover positions six to nine. Segment 3 covers positions two to sixteen; segments 2, 4 12, and 17, positions ten to sixteen; segments 5 6 7 8, positions one to six; segment 11, positions one to five; segment 12, position one; segments 13 13" 13 13, positions five, nine, ten, and sixteen, respectively; segments 14. 14 11 14, positions four, eight, eleven, and fifteen, respectively; segments 15, 15 15and 15, positions three, seven, twelve, and fourteen, respectively; segments 16, 16 and 16, positions two, six, and 13, respectively; segment 18, positions one to sixteen; segment 19, positions one to nine. These segments are cross-connected as follows: segments 1 and 9; 1 3, 5, 7, 11, and 18; 2 and 10; 2 and 12 4, 6, 8, 12, 13, 13 1 1, 1 1 15, 15, 16, 16", and 19; 2, 13, 13, 14, 14, 15, 15, 16 and 17; at and 12.

In the first position of the controller, Fig. 1, the motor-armature MA of the motor-generator is connected across the line and both field-coils of the motor-generator MF GF are 5 excited. This starts the motor-generator.

In the second position, Fig. 2, the generator-field is greatly weakened by the rheostat R, and the generator-armature GA is connected with the armature WA of the work- I00 ing motor, Whose field is excited by the linecurrent. The motor-generator now generates a weak current-say five or ten voltswhich will cause the working motor to start and run slowly at a definite speed.

In the third, fourth, and fifth positions, Figs. 3, 4, and 5, the generator-field is successively strengthened by the cutting out of the rheostat-coils, so that the maximum voltage of the motor-generator current is gradually raised to, say, twenty volts.

The sixth position, Fig. 6, of the controller open-circuits the generator end of the motorgenerator and throws the armature of the working motor across the line through the rheostat. V

In the seventh position, Fig. 7, the motor end of the motor-generator is open-circuited, and the motor-generator stops. The seventh, eighth, and ninth positions, Figs. 7, 8, and 9, gradually increase the speed of the working motor by cutting out the rheostat-coils from its armature-circuit.

In the tenth position, Fig. 10, the working motor is connected with the highpotential main y. In the eleventh position, Fig. 11, the first coil of the rheostat is put in series with the field-coil of the working motor to Weaken its field and increase its speed.

In the thirteenth position, Fig. 13, the motor is running under high-line potential and with greatly weakened field, so that it develops its greatest speed.

In order to avoid connecting in the motorgenerator in the operation of turning ofi the controller to stop the motor, it is preferred to have the controller-cylinder capable of revolving continuously in one direction. To provide for cutting out the resistance from the field-circuit, the segments 15 14 15 are provided in reverse position through the last three steps of the controller, the final step, Fig. 16, being adjacent to the open-circuit position.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. The combination with a working electric motor, of a supply-circuit, a motor-generator, and means for connecting the motor end of the motor-generator with the supply-circuit, and the armature of the generator end with the armature of the working motor in a separate closed circuit, for varying the field strength of the generator end of the motorgenerator, and for finally open-circuiting the motor-generator and connecting the working ture of the working motor in a separate closed circuit, means for varying the field strength of the generator-field of the motor-generator, means for cutting out the motor-generator, and simultaneously throwing the workingmotor armature across the supply-circuit in series with a resistance, means for varying said resistance, means for introducing said resistance in series with the field-coil of said motor, and means for varying said resistance.

3. The combination with a working motor, a motor-generator and a variable resistance, of means for connecting in parallel across the line the motor end of said motor-generator, the field-coil of the generator end and the field-coil of the working motor, means for including the resistance in series with the fieldcoil of the generator end, and means for connecting the armature of the generator end in a closed circuit with the armature of the working motor.

4. The combination with a working motor, a motor-generator and a variable resistance, of means for connecting in parallel across the line the motor end of said motor-generator, the field-coil of the generator end and the field-coil of the Working motor, means for including the resistance in series with the fieldcoil of the generator end, means for connecting the armature of the generator end in a closed circuit with the armature of the working motor, means for cutting out the motorgenerator, and means for cutting the resistance gradually into and then out of the fieldcircuit of the working motor to increase and decrease its speed.

5. The combination with a working motor, of a motor-generator, a variable resistance, and a controller adapted when moved in one direction to connect the motor-generator with the armature of the working motor, cut out the motor-generator and simultaneously put the resistance in series with the armature of the working motor, gradually cut out the resistance and gradually put it in series with the field-coil of said motor, and finally gradually cut it out again and open-circuit the motor.

6. The combination with a motor, of a controller adapted when moved in one direction to cut resistance gradually into series with the field-coil of said motor and then gradually cut it out again before passing on to the OE position.

In witness whereof I have hereunto set my hand this 28th day of March, 1902.

ALBERT G. DAVIS.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

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